Boiler



J KRUG Feb. 7,1939.

BOILER Filed Sept. 19, 1955 ZSheets-Sheet 1 Z w 7 4 m a \g g \v 17 w 7 a.

7 v (1 M m 4/ 1 0 Q Q N M m WM Rw T r m V U /I m m0. J

ATTORNEY J. KR UG' BOILER Feb 7,1939.

Filed Sept. 19, 1935 2 Sheets-Sheet 2 we I } INVENTOR JUL /U.5 /f/?(/6" BY Y ATTORNEY The present invention relates to steam gen- Figure is a diagrammatic view illustrating erators and particularly to cooling screens for the circulation within the cooling screen; and the walls of the furnaces thereof. Figure 6 is an enlarged View illustrating one One object of the present invention is to immanner of connecting the steam risers to the prove the circulation in such boilers. upper header of the cooling screen. 5

Another object is to obtain the maximum pos- In the drawings the numeral l6 designates a fed tothe screen to make up for the steam reed; although the lower portions of tubes 2| exwalls arranged in accordance with the invention; about equal to the difference of the water head 50 UNITED STATES PATENT ()FFICE BOILER.

Julius Krug, Berlin, Germany, assignor to Oombustion Engineering Company, Inc., New York, N. Y.

Application September 19, 1925, Serial No; 41,206

In Germany September 28, 1934 9 Claims. (01. 122235) sible separation of water inthe cooling screen furnace chamber the walls of which are cooled about the furnace from the water circulations by water screens formed of tubes at least partly in other portions of the boiler. exposed to the radiant heat of the gases of com- A third object of the invention is to lessen the bustion. The water screens along the front and 10 cost of the boiler. back walls comprise riser tubes H, I2 connected In accordance with the invention, these objects between a lower transversely disposed header are attained by providing for uniform distribudrum l3 and an upper transverse header drum tion of steam and water and by providing risers l4, these tubes also having portions Ha, I20, from the upper header of the cooling screen extending across the top and bottom respecthat discharge above the water level in the boiler tively, of chamber If]. The side wall screen drum and in which the total loss of head, with tubes l5 are connected into upper and lower substantially dry steam flowing therethrough, headers l6, II that are disposed along the side is substantially equal or about equal to the difwalls. The headers It, 51 are connected in turn ference of the water-head above the elevation of to drums i4 and 13, respectively, by tubes l8, 2&3 the'inlet. of the risers plus the rising force in intermediately bent at right angles and extendthe water walls on one hand minus the resisting across and along the furnace chamber it ance of the downcomers to the walls plus the above and below, respectively, the top tubes Ha resistance to flow in the water walls themselves and bottom tubes l2a. Recirculator tubes 21 on theother hand. extend from upper drum Hi to lower drum l3. l

By this arrangement the water within the The lower drum !3 receives water from the cooling tubes is for the main part retained within boiler drum 22 through downc-omers 23, those the cooling screen so that substantially. only in the arrangement of Figure 5 connecting into steam flows throughthe riser tubes to the boiler the lower water drum M to which the generating drum, and substantially only enough water is tubes 25 and main downcomers 25 are connectleased. Thus, the boiler drum receives from tend across the furnace chamber, they function the screen substantially only steam, so tlfat as recirculators since the vertical portions theresteamingwithin aboiler having other generating of which are connected to drum Id are maintubes is not influenced by the cooling screen. tained cool by the furnace wall and the water Consequently, a cooling screen constructed in head therein causes downward circulation inthe accordance with the invention is particularly direction of the arrows appearing in the drawsuited to boilers which deliver wet steam and ings because the production of steam in these whose furnaces are to be faced with cooling tubes can at most effect a slight reduction in tubes, or whose capacity is to be raised by the the effective water head. The downcomers 23 use of furnace cooling screens in combination and recirculatorsZl are protected by the walls with an increase in the firing capacity. Likewise, 21 or may be screened by the risers H and i2, it is possible by reconstructing existing cooling respectively, as in Figure 4. The upper drum I l screens, in accordance with the teaching of this of the water screen is connected to the boiler invention, to reduce the wetness of steam in a drum 22 at a level above the water line therein unit and/or to improve the operation of the by risers 3|]. boiler. In the drawings: As indicated in Fig. 5 the total loss of head Figure 1 is a vertical sectional; view of a Rin the risers 38, with substantially dry steam boiler having a cooling screen; for the furnace flowing therethrough, is substantially equal or Figures 2 and 3 are sectional views along the P above the elevation of inlet of the risers lines2-2 and 3-3 in Figure 1; plus the rising force in the water walls on one Figure 4 is a view similar to Figure l but showhand minus the resistance of the downcomers ing a lateral oiftake for flue gases rather than R1 to the walls plus the resistance toflow in avertical oneas in Fig. 1; the water walls themselves on the other hand.

In accordance with the invention the risers 30 are carried downwardly into the steam release or upper header [4, as shown in Figure 6, and provided with slits or holes similar to well screens (or the tubes may be out 01f diagonally) whereby a greater projection of risers 30 into the header l4 exposes a greater steam release area. Thus, a water level is obtained in the steam release header H at such a height that resistance through the exposed free areas of the outlet screen 29 and riser tubes 30 equals the pressure head P of the boiler water level above the steam release line in header l4.

When firing is started, the tubes ll, I2, l5 absorb heat from the fire and generate steam which, mixed with water, ascends into risers 30. As the load increases, a water level will be established in drum [4 and only steam Will flow into risers 30 through the basket screen 29 and in time the remaining water is crowded out of the risers, so that eventually only steam flows through them. As a result, at higher loads the Water is driven from the risers 30 and a water level maintained in the upper screen header l4 so that only steam ascends from the screen tubes through risers 30 to the boiler drum 22.

The recirculators 2| return water from header [4 to header l3 and only sufiicient water flows from boiler drum 22 through downcomers 23 to replace that ascending as steam into the boiler drum through risers 30 upon being converted into steam in the water screen. This results in the greatest possible separation of the water circulation in the water screen and in the remaining generating surfaces of the boiler. These circulations may be determined in advance and conflicting flows, as well as stagnation or reversal of flows with consequent overheating of the tube material is avoided. By obviating conflicting flows the resistance to flow circulation is reduced so that circulation in existing boilers may be improved by installing a water screen in accordance with this invention, or for a given circulation the tube areas and/or number of tubes may be reduced, which in addition to cheapening the cooling screen lessens the cost of the boiler.

At low loads and low steam generation the velocity and therewith the resistance within the risers 30 is lower. Consequently, water may be discharged from the cooling screen into the boiler drum. Nevertheless, the arrangements of the present invention have the advantage that the higher the load the higher will be the steam delivered by the boiler and less water will be carried into the drum 22 with the steam whereas usual boiler arrangements deliver relatively wet steam at maximum loads. Furthermore, variations in load have less influence on the cooling screens subjected to radiant heat than on the convection parts of the boiler.

Parallel flow and uniform distribution of water and steam is attained in the entire tube system of the boiler due to the parallel disposition of the feed drum 22 and headers I3, I 4 with respect to each other and because of the connection of the tubes of the several groups into uniformly distributed openings arranged in longitudinal rows along the length of feed drum 22 and headers l3, l4. From the above it follows that in addition to the uniform expansion of the tube system and drums, markedly less resistance to the flow exists in the tube system, so that the circulation is either increased or, for the same circulation, fewer downcomers may be used.

The risers 30 from the cooling screen are led to the steam and water drum 22 within the flu gas ofitake 32 and thus these tubes act as superheater elements and serve to dry the steam and partially superheat it before it arrives in drum 22.

Parallel flow and uniform distribution of feed water between drum 22 and lower header I3 and of steam between upper header l4 and drum 22 (which also serves as the steam drum) is assured by the connection of the downcomers 23 and risers 30 into longitudinal rows of uniformly spaced openings in the header l3, l4 and drum 22. Likewise the connection of the wall tubes II, l2, l5 into the headers I3, [4 results in uniform distribution and parallel flow through the cooling screen. The tubes of various groups of the cooling screen are of nearly the same length so that their portions exposed to the flame absorb substantially the same amount of heat and consequently develop the same velocity of flow.

The uniform distribution of the recirculator tubes 2i connecting the upper header M with the lower header I3 eliminates longitudinal flow of water in header l4 that would offer resistance to the rising currents of steam and water from the wall tubes H, l2 and IS. The connection of the side wall tubes l5 and recirculator tubes 2| into longitudinal rows of openings in header l4 also prevents mutual interference between the flow of the water and steam mixture rising from tubes l I2, l5 and the flow of water separated from steam in header M and returned to drum [3, as has heretofore been the case in other boilers in which steam from side wall tubes entered the end of a steam and water drum and the water recirculated through tubes connecting near the end of the drum.

Further, the feed water drum 22 serves directly as a header for the superheater 33 as well as for the feed water heater tube system 34, so that a parallel flow is also maintained in these tubes, and it is only necessary to have one header 35 for leading off the superheated steam and one header 36 for delivering the feed water to the tube system. The parallel connection of the economizer and superheater tubes to drum 22 assures uniform intensity of flow of water from the economizer into the steam generator as well as of steam to the superheater so that cross flows and resistances in drum 22 are kept to a minimum.

Feed drum 22, as well as upper header drum l4, and the side wall upper headers 16, are supported by the boiler framing 29. The lower drum l3 hangs from tubes 23, which in turn hang from drum 22. The furnace riser tubes ll, [2, l5 are in this way relieved of the Weight of the lower drum and are consequently subject only to the strains which result from heating them. They are thus free from weight strains so that all the risers may expand uniformly.

Incidentally, a boiler embodying the features of the invention may be constructed very cheaply and with a small number of hand hole closures and with greater operating safety since only three drums and two headers are required; one drum serving simultaneously as a steam separator and accumulator and as a header for the superheater and economizer; the other two drums serving to distribute water to the cooling screen and to collect steam therefrom. It may be noted that the cooling tubes along the several walls of the furnace are connected into a common upper drum l4 whereby greater quantities of steam are gathered into the one drum and whereby a more uniform distribution of the risers 30 longitudinally of the headerjas'well as alongthedrum 22 maybe obtained.

What I claim is; l l

1. In a boiler having a furnace chamber; a cooling screen'for twowopposite walls of thelatter comprising a header disposed along the bottom of one wall; a second header disposed along the top of the other wall; circulating'tubes covering the said wallsof said chamber connected into uniformity spaced openingsdisposed longitudinally of said headers and having portions extending over the roof and floor-of said chamber; a steam andwater drum disposed parallel to and above said first mentioned header; downcomers connecting into uniformly spaced openings disposed longitudinally of said drum and first mentioned header; and riser tubes connecting into uniformly spaced openings disposed longitudinally of said other header and said drum.

2. In a boiler having a furnace chamber; a cooling screen for two opposite walls of the latter comprising a water feeding header disposed along the bottom of one wall; a steam collecting header disposed along the top of the other wall; circulating tubes covering the said walls of said chamber connected into uniformly spaced openings disposed longitudinally of said headers and having portions extending over the roof and floor of said chamber; a steam and water drum disposed parallel to and above said first mentioned header; downcomers connecting into uniformly spaced openings disposed longitudinally of said drum and first mentioned header; and riser tubes connecting said steam collecting header to said steam and water drum, said tubes being disposed in the path of gases from said chamber and serving as superheater tubes for steam passing from said header to said drum.

3. In a boiler having a furnace chamber; a cooling screen for the walls of the latter comprising, a lower header disposed along the bottom of one wall; an upper header disposed along the top of the opposite wall; circulating tubes covering the front and back walls of said chamber connected into uniformly spaced openings disposed longitudinally of said headers and having portions extending over the roof and floor of said chamber; a steam and water drum disposed parallel to and above said lower header; downcomers connecting into uniformly spaced openings disposed longitudinally of said drum and lower header; circulating tubes covering the opposite side walls of said chamber; uniformly spaced circulators connected with said side wall tubes and extending across and along the top and bottom, respectively, of said chamber to said upper and lower headers, respectively; and risers common to all said walls connecting said upper header to said steam and water drum.

4. In a boiler having a furnace chamber; a cooling screen for opposite walls of the latter comprising a header disposed along the bottom of one wall; a second header disposed along the top of the other wall; circulating tubes covering the said walls of said chamber connected into uniformly spaced openings disposed longitudinally of said headers and having portions extending over the roof and floor of said chamber; a steam and water drum disposed parallel to and above said first mentioned header; downcomers connecting into uniformly spaced openings disposed longitudinally of said drum and first mentioned header; and a superheater and an economizer having one end of each heat absorbing element thereof directly connected into uniformly spaced openings disposed longitudinally of said steam and water drum.

5. -In a boiler having a frame; a steam and water drum supported thereon; a furnace chamber;

watercirculatingtubes covering one pair of oppositewallsthereof and having portions extending over the roof andfloor of said chamber; an upper header supported in the frame to which said tubes are connected atone end; a lower header to whichsaid tubes are connected at the opposite end; downcomers connected between said drum and lower header and supporting the latter;

and riser tubes connecting said upper header to said drum.

6. In a boiler having a frame; a steam and water drum supported thereon; a furnace chamber; water circulating tubes covering one pair of opposite walls thereof and having portions extending over the roof and floor of said chamber; an upper header supported in the frame to which said tubes are connected at one end; a lower header to which said tubes are connected at the opposite end; downcomers connected between said drum and lower header and supporting the latter; riser tubes connecting said upper header to said drum; and tubes covering the side walls of said chamber and connected into upper headers supported in the frame and lower headers adjacent the bottom of said chamber.

7. In a boiler having a frame; 'a steam and water drum supported thereon; a furnace chamber; water circulating tubes covering the front and back walls thereof and having portions extending over the roof and floor of said chamber; an upper header supported in the frame to which said tubes are connected at one end; a lower header to which said tubes are connected at the opposite end; downcomers connected between said drum and lower header and supporting the latter; riser tubes connecting saidupper header to said drum; tubes covering the side walls of said chamber and connected into upper headers supported in the frame and lower headers adjacent the bottom of said chamber; and bent tubes covering the top and bottom of said chamber and connected between the headers for said side wall tubes and the upper and lower headers, respectively, for the front and back wall tubes.

8. In a boiler having a furnace chamber; a cooling screen for the walls of the latter comprising, a lower header disposed along the bottom of one wall; an upper header disposed along the top of the opposite wall; circulating tubes on said walls of said chamber connected into uniformly spaced openings disposed longitudinally of said headers and having portions extending over the roof and floor of said chamber; a steam and water drum disposed parallel to and above said lower header; downcomers connected into uniformly spaced openings disposed longitudinally of said drum and lower header; tubes covering opposite side walls of said chamber; circul'ator tubes communicating with the upper and lower ends of said side wall tubes and extending across and along the top and bottom, respectively, of said chamber to said upper and lower headers, respectively, said side wall tubes and circulators forming parallel circuits of substantially equal length from said lower header to said upper header; and risers common to all said wall tubes connecting said upper header to said steam and water drum.

9. In a boiler having a furnace chamber; a cooling screen for the walls of the latter comprising; a lower header disposed along the bottom of one wall; an upper header disposed along the top of the opposite wall; circulating tubes on said walls of said chamber connected into uniformly spaced openings disposed longitudinally of said headers and having portions extending over the roof and floor of said chamber; circulating tubes covering opposite side walls of said chamber; circulators communicating with the ends of said side wall tubes and extending across and along the top and bottom, respectively, of said chamber to said upper and lower headers, respectively, said side wall tubes and circulators forming parallel circuits of substantially equal length between said lower header and said upper header; a steam and water drum disposed above said headers; downcomers connecting said drum with said lower header for supplying feedwater to said screen tubes; risers connecting said upper header and said drum, said risers resisting the flow of fluid from said headers to said drum to the extent that substantially only steam passes from said header to said drum; and recirculator tubes connecting said headers for returning to said lower header the Water separated in said upper header from the steam and Water mixture entering said upper header from said wall tubes.

JULIUS KRUG. 

